10 Common Django Mistakes That Can Ruin Your App (And How to Fix Them!)

Django is a powerful and developer-friendly framework, but even experienced developers can make critical mistakes that impact performance, security, and maintainability. If you don’t follow best practices, you could end up with slow queries, security vulnerabilities, and difficult-to-maintain code.

In this article, we’ll cover 10 common Django mistakes that can ruin your app – and how to fix them!

1. Not Using Django’s Built-in Security Features

Django comes with built-in security protections, but many developers either disable them or forget to use them.

🚨 Common Mistakes:

❌ Disabling CSRF protection

CSRF_COOKIE_SECURE = False

❌ Not using Django’s authentication system (User.objects.create(…) instead of User.objects.create_user(…)).

❌ Storing passwords in plain text.

✅ Fix:

• Always enable CSRF protection ({% csrf_token %} in forms).

• Use User.objects.create_user(username, password) to hash passwords properly.

• Set SECURE settings in settings.py:

CSRF_COOKIE_SECURE = True 
SESSION_COOKIE_SECURE = True 
SECURE_BROWSER_XSS_FILTER = True 
SECURE_CONTENT_TYPE_NOSNIFF = True

2. Not Optimizing Database Queries (N+1 Problem)

If you’re not careful, Django’s ORM can generate too many queries, slowing down your app.

🚨 Common Mistakes:

❌ Using .all() and looping over results, causing N+1 queries.

❌ Fetching unnecessary fields.

❌ Not using indexes.

✅ Fix:

• Use select_related() for foreign key relationships to avoid extra queries:

books = Book.objects.select_related('author').all()

• Use only() and defer() to fetch only necessary fields:

books = Book.objects.only('title', 'published_date').all()

• Use prefetch_related() for many-to-many relationships:

books = Book.objects.prefetch_related('genres').all()

3. Hardcoding Sensitive Information in settings.py

Never store API keys, database credentials, or secret keys directly in settings.py. If you push your code to a public repo, you risk leaking private data.

🚨 Common Mistakes:
❌ Storing credentials like this:

# settings.py 
SECRET_KEY = "my-secret-key" 
DATABASES = { 
    'default': { 
        'ENGINE': 'django.db.backends.postgresql', 
        'NAME': 'mydb', 
        'USER': 'admin', 
        'PASSWORD': 'mypassword', 
    } 
}

✅ Fix:

• Use environment variables and django-environ:

# settings.py 
import environ 
 
env = environ.Env() 
environ.Env.read_env()  # Reads from .env file 
 
SECRET_KEY = env("SECRET_KEY") 
DATABASES = { 
    'default': { 
        'ENGINE': 'django.db.backends.postgresql', 
        'NAME': env("DB_NAME"), 
        'USER': env("DB_USER"), 
        'PASSWORD': env("DB_PASSWORD"), 
    } 
}

• Store sensitive values in a .env file (and add it to .gitignore):

4. Using print() for Debugging Instead of Logging

Debugging with print() makes your code messy and hard to track in production.

🚨 Common Mistakes:
❌ Scattering print() statements everywhere.
❌ No logging setup.

✅ Fix:

• Use Django’s built-in logging system in settings.py :

# settings.py 
LOGGING = { 
    'version': 1, 
    'disable_existing_loggers': False, 
    'handlers': { 
        'file': { 
            'level': 'DEBUG', 
            'class': 'logging.FileHandler', 
            'filename': 'debug.log', 
        }, 
    }, 
    'loggers': { 
        'django': { 
            'handlers': ['file'], 
            'level': 'DEBUG', 
            'propagate': True, 
        }, 
    }, 
}

• Use logging.debug() instead of print():

# views.py 
import logging 
logger = logging.getLogger(__name__) 
 
def my_view(request): 
    logger.debug("This is a debug message")

5. Not Handling Media Files Correctly

If you serve media files incorrectly, users may not see uploaded images or files.

🚨 Common Mistakes:
❌ Storing media files in /static/ instead of /media/.
❌ Not setting MEDIA_URL and MEDIA_ROOT properly.

✅ Fix:

• Configure media settings in settings.py :

# settings.py 
MEDIA_URL = '/media/' 
MEDIA_ROOT = BASE_DIR / 'media'

• Configure urls.py for development mode:

# urls.py 
from django.conf import settings 
from django.conf.urls.static import static 
 
urlpatterns = [ 
    # Your other URLs 
] + static(settings.MEDIA_URL, document_root=settings.MEDIA_ROOT)

• Use cloud storage (AWS S3, Google Cloud Storage) in production.

6. Using Django Admin as the Only Admin Panel

Django Admin is not designed for end-users. Exposing it publicly is a security risk.

🚨 Common Mistakes:
❌ Relying only on Django Admin for backend operations.
❌ Not restricting access to Django Admin.

✅ Fix:

• Use staff_required decorators for custom dashboards.
• Restrict admin access:

# views.py 
from django.contrib.admin.views.decorators import staff_member_required 
 
@staff_member_required 
def my_admin_view(request): 
    ...

• Use third-party admin panels like django-grappelli or django-jazzmin for better customization.

7. Not Using Django Signals Wisely

Django signals can be useful, but misusing them can slow down your app.

🚨 Common Mistakes:
❌ Running expensive database queries inside signals.
❌ Using signals for things better handled in views or tasks.

✅ Fix:

• Use Celery for background tasks instead of signals.
• Use signals only for lightweight tasks like caching.

8. Poor Caching Strategy

If you don’t use caching, your app can become slow under heavy traffic.

🚨 Common Mistakes:
❌ Not caching expensive queries.
❌ Using cache_page() without proper expiration.

✅ Fix:

• Use Django’s caching framework:

from django.core.cache import cache 
 
data = cache.get('my_data') 
if not data: 
    data = expensive_query() 
    cache.set('my_data', data, timeout=3600)

• Use Redis or Memcached for faster performance.

9. Ignoring Performance Bottlenecks

🚨 Common Mistakes:
❌ Loading too many database queries per request.
❌ Using too many serializers and nested relationships.

✅ Fix:

• Use Django Debug Toolbar to detect slow queries.
• Optimize Django ORM queries using select_related() and prefetch_related().

10. Not Writing Tests

Without tests, you won’t know when something breaks.

🚨 Common Mistakes:
❌ No unit tests or integration tests.
❌ Only testing in production.

✅ Fix:

• Write unit tests using Django’s TestCase.
• Use pytest-django for better testing.

Final Thoughts

By avoiding these 10 common Django mistakes, you’ll build faster, more secure, and maintainable applications. Django is a powerful framework, but like any tool, how you use it makes all the difference!

Did you find this helpful? Let me know in the comments! 🚀